certain and incontrovertible, the exact manner in which they happened
may remain unknown, without prejudicing the conclusions that may be
drawn from them; nevertheless, by a little reflection, we shall find at
least plausible reasons for these changes. We daily observe the sea
gaining ground on some coasts and losing it on others; we know that the
ocean has a continued regular motion from East to West; that it makes
loud and violent efforts against the low lands and rocks which confine
it; that there are whole provinces which human industry can hardly
secure from the rage of the sea; that there are instances of islands
rising above, and others being sunk under the waters. History speaks of
much greater deluges and inundations. Ought not this to incline us to
believe that the surface of the earth has undergone great revolutions,
and that the sea may have quitted the greatest part of the earth which
it formerly covered? Let us but suppose that the old and new worlds were
formerly but one continent, and that the Atlantis of Plato was sunk by
a violent earthquake; the natural consequence would be, that the sea
would necessarily have flowed in from all sides, and formed what is now
called the Atlantic Ocean, leaving vast continents dry, and possibly
those which we now inhabit. This revolution, therefore, might be made of
a sudden by the opening of some vast cavern in the interior part of the
globe, which an universal deluge must inevitably succeed; or possibly
this change was not effected at once, but required a length of time,
which I am rather inclined to think; however these conjectures may be,
it is certain the revolution has occurred, and in my opinion very
naturally; for to judge of the future, as well as the past, we must
carefully attend to what daily happens before our eyes. It is a fact
clearly established by repeated observations of travellers, that the
ocean has a constant motion from the East to West; this motion, like the
trade winds, is not only felt between the tropics, but also throughout
the temperate climates, and as near the poles as navigators have gone;
of course the Pacific Ocean makes a continual effort against the coasts
of Tartary, China, and India; the Indian Ocean acts against the east
coast of Africa; and the Atlantic in like manner against all the eastern
coasts of America; therefore the sea must have always and still
continues to gain land on the east and lose it on the west; and this
alone is sufficient to prove the possibility of the change Of earth into
sea, and sea into land. If, in fact, such are the effects of the sea's
motion from east to west, may we not very reasonably suppose that Asia
and the eastern continent is the oldest country in the world, and that
Europe and part of Africa, especially the western coasts of these
continents, as Great Britain, France, Spain, Muratania, &c. are of a
more modern date? Both history and physics agree in confirming this
conjecture.
There are, however, many other causes which concur with the continual
motion of the sea from east to west, in producing these effects.
In many places there are lands lower than the level of the sea, and
which are only defended from it by an isthmus of rocks, or by banks and
dykes of still weaker materials; these barriers must gradually be
destroyed by the constant action of the sea, when the lands will be
overflowed, and constantly make part of the ocean. Besides, are not
mountains daily decreasing by the rains, which loosen the earth, and
carry it down into the vallies? It is also well known that floods wash
the earth from the plains and high grounds into the small brooks and
rivers, which in their turn convey it into the sea. By these means the
bottom of the sea is filling up by degrees, the surface of the earth
lowering to a level, and nothing but time is necessary for the sea's
successively changing places with the earth.
I speak not here of those remote causes which stand above our
comprehension; of those convulsions of nature, whose least effects would
be fatal to the world; the near approach of a comet, the absence of the
moon, the introduction of a new planet, &c. are suppositions on which it
is easy to give scope to the imagination. Such causes would produce any
effects we chose, and from a single hypothesis of this nature, a
thousand physical romances might be drawn, and which the authors might
term, THE THEORY OF THE EARTH. As historians we reject these vain
speculations; they are mere possibilities which suppose the destruction
of the universe, in which our globe, like a particle of forsaken matter,
escapes our observation, and is no longer an object worthy regard; but
to preserve consistency, we must take the earth as it is, closely
observing every part, and by inductions judge of the future from what
exists at present; in other respects we ought not to be affected by
causes which seldom happen, and whose effects are always sudden and
violent; they do not occur in the common course of nature; but effects
which are daily repeated, motions which succeed each other without
interruption, and operations that are constant, ought alone to be the
ground of our reasoning.
We will add some examples thereto; we will combine particular effects
with general causes, and give a detail of facts which will render
apparent, and explain the different changes that the earth has
undergone, whether by the eruption of the sea upon the land, or by
retiring from that which it had formerly covered.
The greatest eruption was certainly that which gave rise to the
Mediterranean sea. The ocean flows through a narrow channel between two
promontories with great rapidity, and then forms a vast sea, which,
without including the Black sea, is about seven times larger than the
kingdom of France. Its motion through the straits of Gibraltar is
contrary to all other straits, for the general motion of the sea is from
east to west, but in that alone it is from the west to the east, which
proves that the Mediterranean sea is not an ancient gulph, but that it
has been formed by an eruption, produced by some accidental cause; as an
earthquake which might swallow up the earth in the strait, or by a
violent effort of the ocean, caused by the wind, which might have forced
its way through the banks between the promontories of Gibraltar and
Ceuta. This opinion is authorised by the testimony of the ancients, who
declare in their writings, that the Mediterranean sea did not formerly
exist; and confirmed by natural history and observations made on the
opposite coasts of Spain, where similar beds of stones and earth are
found upon the same levels, in like manner as they are in two mountains,
separated by a small valley.
The ocean having forced this passage, it ran at first through the
straits with much greater rapidity than at present, and overflowed the
continent that joined Europe to Africa. The waters covered all the low
countries, of which we can only now perceive the tops of some of the
considerable mountains, such as parts of Italy, the islands of Sicily,
Malta, Corsica, Sardinia, Cyprus, Rhodes, and those of the Archipelago.
In this eruption I have not included the Black sea, because the quantity
of water it receives from the Danube, Nieper, Don, and various other
rivers, is fully sufficient to form and support it; and besides, it
flows with great rapidity through the Bosphorus into the Mediterranean.
It might also be presumed that the Black and Caspian seas were formerly
only two large lakes, joined by a narrow communication, or by a morass,
or small lake, which united the Don and the Wolga near Tria, where these
two rivers flow near each other; nor is it improbable that these two
seas or lakes were then of much greater extent, for the immense rivers
which fall into the Black and Caspian seas may have brought down a
sufficient quantity of earth to shut up the communication, and form that
neck of land by which they are now separated; for we know great rivers,
in the course of time, fill up seas and form new land, as the province
at the mouth of the Yellow river in China; Louisania at the mouth of the
Mississippi, and the northern part of Egypt, which owes its existence to
the inundations of the Nile; the rapidity of which brings down such
quantities of earth from the internal parts of Africa, as to deposit on
the shores, during the inundations, a body of slime and mud of more than
fifty feet in depth. The province of the Yellow river and Louisania
have, in like manner, been formed by the soil from the rivers.
The Caspian sea is actually a real lake; having no communication with
other seas, not even with the lake Aral, which seems to have been a part
of it, being only separated from it by a large track of sand, in which
neither rivers nor canals for communication the waters have as yet been
found. This sea, therefore, has no external communication with any
other; and I do not know that we are authorised to suspect that it has
an internal one with the Black sea, or with the Gulph of Persia. It is
true the Caspian sea receives the Wolga and many other rivers, which
seem to furnish it with more water than is lost by evaporation; but
independent of the difficulty of such calculation, if it had a
communication with any other sea, a constant and rapid current towards
the opening would have marked its course, and I never heard of any such
discovery being made; travellers of the best credit affirm to the
contrary, and consequently the Caspian sea must lose by evaporation just
as much water as it receives from the Wolga and other rivers.
Nor is it any improbable conjecture that the Black sea will at some
period be separated from the Mediterranean; and that the Bosphorus will
be shut up, whenever the great rivers shall have accumulated a
sufficient quantity of earth to answer that effect; this may be the case
in the course of time by the successive diminution of waters in rivers,
in proportion as the mountains from whence they draw their sources are
lowered by the rains, and those other causes we have just alluded to.
The Caspian and Black seas must therefore be looked upon rather as lakes
than gulphs of the ocean, for they resemble other lakes which receive a
number of rivers without any apparent outlet, such as the Dead sea,
many lakes in Africa and other places. These two seas are not near so
salt as the Mediterranean or the ocean; and all voyagers affirm that the
navigation in the Black and Caspian seas, upon account of its
shallowness and quantity of rocks and quicksands, is so extremely
dangerous, that only small vessels can be used with safety which farther
proves they must not be looked upon as gulphs of the ocean, but as
immense bodies of water collected from great rivers.
A considerable eruption of the sea would doubtless take place upon the
earth, if the isthmus which separates Africa from Asia was divided, as
the Kings of Egypt, and afterwards the Caliphs projected; and I do not
know that the communication between the Red sea and Mediterranean is
sufficiently established, as the former must be higher than the latter.
The Red sea is a narrow branch of the ocean, and does not receive into
it a single river on the side of Egypt, and very few on the opposite
coast; it will not therefore be subject to diminution, like those seas
and lakes which are constantly receiving slime and sand from those
rivers that flow into them. The ocean supplies the Red sea with all its
water, and the motion of the tides is very evident in it, of course it
must be affected by every movement of the ocean. But the Mediterranean
must be lower than the ocean, because the current passes with great
rapidity through the straits; besides, it receives the Nile, which flows
parallel to the west coast of the Red sea, and which divides Egypt, a
very low country; from all which it appears probable, that the Red sea
is higher than the Mediterranean, and that if the isthmus of Suez was
cut through, there Would be a great inundation, and a considerable
augmentation of the Mediterranean would ensue; at least if the waters
were not restrained by dykes and sluices placed at proper distances, and
which was most likely the case if the ancient canal of communication
ever had existence.
Without dwelling longer upon conjectures, which, although well founded,
may appear hazardous and rash, we shall give some recent and certain
examples of the change of the sea into land, and the land into sea. At
Venice the bottom of the Adriatic is daily rising, and if great care had
not been taken to clean and empty the canals, the whole would long
since have formed part of the continent; the same may be said of most
ports, bays, and mouths of rivers. In Holland the bottom of the sea has
risen in many places; the gulph of Zuyderzee and the strait of the Texel
cannot receive such large vessels as formerly. At the mouth of all
rivers we find small islands, and banks of sand and earth brought down
by the waters, and it is certain the sea will be filled up in every part
where great rivers empty themselves. The Rhine is lost in the sands
which itself accumulated. The Danube and the Nile, and all great rivers,
after bringing down much sand and earth, no longer come to the sea by a
single channel; they divide into different branches, and the intervals
are filled up by the materials they have themselves brought thither.
Morasses daily dry up; lands forsaken by the sea are cultivated; we
navigate countries now covered by waters; in short, we see so many
instances of land changing into water, and water into land, that we must
be convinced of these alterations having, and will continue to take
place; so that in time gulphs will become continents; isthmusses,
straits; morasses, dry lands; and the tops of our mountains, the shoals
of the sea.
Since then the waters have covered, and may successively cover, every
part of the present dry land, our surprise must cease at finding every
where marine productions and compositions, which could only be the works
of the waters. We have already explained how the horizontal strata of
the earth were formed, but the perpendicular divisions that are commonly
found in rocks, clays, and all matters of which the globe is composed,
still remain to be considered. These perpendicular stratas are, in fact,
placed much farther from each other than the horizontal, and the softer
the matter the greater the distance; in marble and hard earths they are
frequently found only a few feet; but if the mass of rock be very
extensive, then these fissures are at some fathoms distant; sometimes
they descend from the top of the rock to the bottom, and sometimes
terminate at an horizontal fissure. They are always perpendicular in the
strata of calcinable matters, as chalk, marle, marble, &c. but are more
oblique and irregularly placed in vitrifiable substances, brown
freestone, and rocks of flint, where they are frequently adorned with
chrystals, and other minerals. In quarries of marble or calcinable
stone, the divisions are filled with spar, gypsum, gravel, and an earthy
sand, which contains a great quantity of chalk. In clay, marls, and
every other kind of earth, excepting turf, these perpendicular divisions
are either empty or filled with such matters as the water has
transported thither.
We need seek very little farther for the cause and origin of those
perpendicular cracks. The materials by which the different strata are
composed being carried by the water, and deposited as a kind of
sediment, must necessarily, at first, contain a considerable share of
water, the which, as they began to harden, they would part with by
degrees, and, as they must necessarily lessen in the course of drying,
that decrease would occasion them to split at irregular distances. They
naturally split in a perpendicular direction, because in that direction
the action of gravity of one particle upon another has no actual effect,
while, on the contrary, it is directly opposite in a horizontal
situation; the diminution of bulk therefore could have no sensible
effect but in a vertical line. I say it is the diminution of drying, and
not the contained water forcing a place to issue, is the cause of these
perpendicular fissures, for I have often observed that the two sides of
those fissures answer throughout their whole height, as exactly as two
sides of a split piece of wood; their insides are rough and irregular,
whereas if they had been made by the motion of the water, they would
have been smooth and polished; therefore these cracks must be produced
suddenly and at once or by degrees in drying, like the flaws in wood,
and the greatest part of the water they contained evaporated through the
pores. The divisions of these perpendicular cracks vary greatly as to
the extent of their openings; some of them being not more than half an
inch, others increasing to one or two feet; there are some many fathoms,
and which form those precipices so often met with in the Alps and other
high mountains. The small ones are produced by drying alone, but those
which extend to several feet are the effects of other causes; for
instance, the sinking of the foundation on one side while the other
remains unmoved; if the base sinks but a line or two, it is sufficient
to produce openings of many feet in a rock of considerable height.
Sometimes rocks, which are founded on clay or sand, incline to one
side, by which motion the perpendicular cracks become extended.
I have not yet mentioned those large openings which are found in rocks
and mountains; they must have been produced by great sinkings, as of
immense caverns, unable longer to support the weight with which they
were encumbered, but these intervals are very different from
perpendicular fissures; they appear to be vacancies opened by the hand
of Nature for the communication of nations. In this manner all vacancies
in large mountains and divisions, by straits in the sea, seem to present
themselves; such as the straits of Thermopylæ, the ports of Caucasus,
the Cordeliers, the extremity of the straits of Gibraltar, the entrance
of the Hellespont, &c. These could not have been occasioned by the
simple separation by drying of matter, but by considerable parts of the
lands themselves being sunk, swallowed up, or overturned.
These great sinkings, though produced by accidental causes, hold a first
place in the principal circumstances in the History of the Earth, and
not a little contributed to change the face of the Globe; the greatest
part of them have been produced by subterraneous fires, whose
explosions cause earthquakes and volcanos; the force of these inflamed
and confined matters in the bowels of the earth is beyond compare; by it
cities have been swallowed up, provinces overturned, and mountains
overthrown. But however great this force may be, and prodigious as the
effects appear, we cannot assent to the opinion of those authors who
suppose these subterraneous fires proceed from an immense abyss of flame
in the centre of the earth, neither give we credit to the common notion
that they proceed from a great depth below the surface of the earth, air
being absolutely necessary for the support of inflammation. In examining
the materials which issue from volcanos, even in the most violent
eruptions, it appears very plain, that the furnace of the inflamed
matters is not at any great depth, as they are similar to those found in
mountains, disfigured only by the calcination, and the melting of the
metallic parts which they contain; and to be convinced that the matters
cast out by volcanos do not come from any great depth, we have only to
consider of the height of the mountain, and judge of the immense force
that would be necessary to cast up stones and minerals to the height of
half a league; for Ætna, Hecla, and many other volcanos have at least
that elevation from the plains. Now it is perfectly well known that the
action of fire is equal in every direction; it cannot therefore act
upwards, with a force capable of throwing large stones half a league
high, without an equal re-action downwards, and on the sides, and which
re-action must very soon pierce and destroy the mountain on every side,
because the materials which compose it are not more dense and firm than
those thrown out; how then can it be imagined that the cavity, which
must be considered as the type or cannon, could resist so great a force
as would be necessary to raise those bodies to the mouth of the volcano?
Besides, if this cavity was deeper, as the external orifice is not
great, it would be impossible for so large a quantity of inflamed and
liquid matter to issue out at once, without clashing against each other,
and against the sides of the tube, and by passing through so long a
space they would run the chance of being extinguished and hardened. We
often see rivers of bitumen and melted sulphur, thrown out of the
volcanos with stones and minerals, flow from the tops of the mountains
into the plains; is it natural to imagine that matters so fluid, and so
little able to resist violent action, should be elevated from any great
depth? All the observations that can be made on this subject will prove
that the fire of the volcano is not far from the summit of the mountain,
and that it never descends to the level of the plain.
This idea of volcanos does not, however, render it inconsistent that
they are the cause of earthquakes, and that their shocks may be felt on
the plains to very considerable distances; nor that one volcano may not
communicate with another by means of subterraneous passages; but it is
of the depth of the fire's confinement that we now speak, and which can
only be at a small distance from the mouth of the volcano. It is not
necessary to produce an earthquake on a plain, that the bottom of the
volcano should be below the level of that plain; nor that there should
be internal cavities filled with the same combustible matter, for a
violent explosion, such as generally attends an eruption, may, like that
of a powder magazine give so great a shock by its re-action, as to
produce an earthquake that might be felt at a considerable distance.
I do not mean to say that there are no earthquakes produced by
subterraneous fires, but merely that there are some which proceed only
from the explosion of volcanos. In confirmation of what has been
advanced on this subject, it is certain that volcanos are seldom met
with on plains; on the contrary, they are constantly found in the
highest mountains, and their mouths at the very summit of them. If the
internal fires of the volcanos extended below the plains, would not
passages be opened in them during violent eruptions? In the first
eruption would not these fires rather have pierced the plains, where, by
comparison, the resistance must be infinitely weaker, than force their
way through a mountain more than half a league in height.
The reason why volcanos appear alone in mountains, is, because much
greater quantities of minerals, sulphur, and pyrites, are contained in
mountains, and more exposed than in the plains; besides which, those
high places are more subject to the impressions of air, and receive
greater quantities of rain and damps, by which mineral substances are
capable of being heated and fermented into an absolute state of
inflammation.
In short, it has often been observed, that, after violent eruptions, the
mountains have shrunk and diminished in proportion to the quantity of
matter which has been thrown out; another proof that the volcanos are
not situated at the bottom of the mountain, but rather at no great
distance from the summit itself.
In many places earthquakes have formed considerable hollows, and even
separations in mountains; all other inequalities have been produced at
the same time with the mountains themselves by the currents of the sea,
for in every place where there has not been a violent convulsion, the
strata of the mountains are parallel, and their angles exactly
correspond. Those subterraneous caverns which have been produced by
volcanos are easily to be distinguished from those formed by water; for
the water, having washed away the sand and clay with which they are
filled, leaves only the stones and rocks, and this is the origin of
caverns upon hills; while those found upon the plains are commonly
nothing but ancient pits and quarries, such as the salt quarries of
Maestricht, the mines of Poland, &c. But natural caverns belong to
mountains: they receive the water from the summit and its environs, from
whence it issues over the surface wherever it can obtain a passage; and
these are the sources of springs and rivers, and whenever a cavern is
filled by any part falling in, an inundation generally ensues.
From what we have related, it is easy to be seen how much subterraneous
fires contribute to change the surface and internal part of the globe.
This cause is sufficiently powerful to produce very great effects: but
it is difficult to conceive how the winds should occasion any sensible
alterations upon the earth. The sea appears to be their empire, and
indeed, excepting the tides, nothing has so powerful an influence upon
the ocean; even the flux and reflux move in an uniform manner, and their
effects are regularly the same; but the action of the winds is
capricious and violent; they sometimes rush on with such impetuosity,
and agitate the sea with such violence, that from a calm, smooth, and
tranquil plain, it becomes furrowed with waves rolling mountains high,
and dashing themselves to pieces against the rocks and shores. The winds
cause constant alterations on the surface of the sea, but the surface of
the land, which has so solid an appearance, we should suppose would not
be subject to similar effects; by experience, however, it is known that
the winds raise mountains of sand in Arabia and Africa; and that they
cover plains with it; they frequently transport sand to great distances,
and many miles into the sea, where they accumulate in such quantities as
to form banks, downs, and even islands. It is also known that hurricanes
are the scourge of the Antilles, Madagascar, and other countries, where
they act with such fury, as to sweep away trees, plants, and animals,
together with the soil which gave them subsistence: they cause rivers to
ascend and descend, and produce new ones; they overthrow rocks and
mountains; they make holes and gulphs on the earth, and entirely change
the face of those unfortunate countries where they exist. Happily there
are but few climates exposed to the impetuosity of those dreadful
agitations of the air.